1. Field of the Invention
The present invention relates to a disk access device that accesses a disk on which recording is performed according to the ZCLV (Zone Constant Linear Velocity) format or the like, and in particular to head control technology for preventing tracking errors.
2. Related Art
DVD-RAM (Digital Versatile Disk Random Access Memory) disks are characterized by being high-capacity disks on which reading, writing and erasing can be performed. Due to density growth, recording is performed in both lands and grooves that are alternately switched on each revolution of a disk to form a single spiral.
Also, recording at a single data rate across the entire disk is enabled by employing, for example, the ZCLV format in which the disk is divided into a plurality of zones that each include a plurality of tracks, and rotation control is performed according to each of the zones.
Inner and outer peripheries of the zones are provided with guard track zones composed of non-recording tracks in order to prevent a light spot from unintendedly entering an adjacent zone.
However, there are cases in which a tracking error occurs at a zone boundary track, which is the outermost portion of a guard track zone, due to the light spot being influenced by the adjacent zone.
In view of this, there is disclosed technology for preventing the light spot from entering the zone boundary track by, for example, jumping to the next zone from two tracks before the zone boundary track (see Japanese Patent Application Publication No. H11-110763).
However, in recent years disk rotation speeds have been increasing along with the rise in recording/playback speeds. There are now cases in which a greater-than-expected number of tracks pass while performing control setting for access to the next zone, as a result of which the light spot enters the zone boundary track. For example, if control setting is not completed before reaching two tracks before the zone boundary track, the light spot will enter the zone boundary track before jumping to the next zone.